1. Field of the Invention
The present invention relates to a two-dimensional calibrating device. More specifically, it relates to a two-dimensional lattice calibrating device that calibrates a mark position of an artifact (e.g. square lattice) as a standard gauge. The present invention also relates to a two-dimensional lattice calibrating method, two-dimensional lattice calibrating program and a recording medium storing the program.
2. Description of Related Art
Conventionally, block-shaped and plate-shaped standard gauges have been used for calibrating a precise measuring instrument. Among such standard gauges, those having square-lattice marks (including measuring point, center of a ball and the like) such as a ball plate and a grid plate are called as artifacts, which are used as a standard mainly for calibrating a coordinate measuring machine and a vision measuring machine. Accordingly, the position of the marks has to be sufficiently accurately positioned. However, it accompanies a great difficulty to produce a highly accurate artifact. Accordingly, after producing an artifact, a deviation between the position of the mark and a nominal position of the mark is measured, calculated and calibrated. In order to calibrate a ball plate, for example, inverse method has been proposed. According to the inverse method, a ball plate is rotated by 180 degrees around x, y and z axes respectively, where total four measurements are conducted to obtain measurement values in accordance with a rank of simultaneous equations for calibration (FIGS. 23A to 23D). However, the inverse method requires that an artifact can be measured from a backside thereof. Accordingly, when it is difficult for an artifact to be measured from a backside, calibration using the inverse method is impractical. For instance, a grid plate (an artifact for vision measuring machine) cannot be highly calibrated by the inverse method, since the condition varies between top-side measurement and backside measurement of the grid plate. Document 1 (“Calibration to Indicate Reference Values for Ball Plate Using CMM” Takeshi WAGO and Isao YONEKURA, Journal of Iwate Industrial Research Institute, No. 12, 2005)